Call the destination, and ask for directions

Define your goal (your final destination) - then contact someone who's there, and ask how to get there.

If you want to be in Rolling Stone magazine, pick up the phone, call their main office in New York City, and when the receptionist answers, say "Editorial, please." Ask someone in the editorial department which publicists they recommend. Then call each publicist, and try to get their attention. (Hint: Don't waste Rolling Stone's time asking for the publicist's phone number. You can find it elsewhere. Get off the phone as soon as possible.)

If you want to play at the biggest club in town, bring a nice box of fancy German cookies to the club booker, and ask for just 5 minutes of their advice. Ask them what criteria must be met in order for them to take a chance on an act. Ask what booking agents they recommend, or if they recommend using one at all. Again, keep your meeting as short as possible. Get the crucial info, then leave them alone. (Until you're back, headlining their club one day!)

I know an artist manager of a small unsigned act, who over the course of a year, met with the managers of U2, REM, and other top acts. She asked them for their advice, coming from the top, and got great suggestions that she's used with big results.

In other words:
Call the destination, and ask for directions.
You'll get there much faster than just blindly walking out your front door, hoping you arrive someday.